Keywords: Lithiation / Substituent effects / Benzophenones / 1,3-Dioxolanes 2-Aryl-2-(chloroaryl)-1,3-dioxolanes 4 were lithiated ortho to the ketal group of the chloroaryl ring by treatment with butyllithium in THF between −78 and 0°C. The site selectivity of some of the deprotonation reactions was rationalized by the long-range effect of the 4-chloro substituent. The lithio species thus generated were treated with various elec-
ortho‐(2‐Aryl‐1,3‐dioxolan‐2‐yl)benzenesulfonyl chlorides obtained from benzophenone ketals by directed ortho‐lithiation chemistry were cyclized either with hydrazine monohydrate or with acetohydrazide to furnish variously substituted 4‐aryl‐2H‐1,2,3‐benzothiadiazine 1,1‐dioxides. Alkylation of benzothiadiazine dioxides with alkyl iodides under basic conditions was elaborated, revealing significant differences compared to the reactivity of 4‐unsubstituted ones. Hydrogenation of the C=N double bond in the presence of platinum(IV) oxide is also described. Detailed NMR studies and DFT calculations supported the structure elucidation of the compounds.
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